WASHINGTON — A classified military report detailing the Army’s investigation into the disappearance of Sgt. Bowe Bergdahl in June 2009 says he had wandered away from assigned areas before — both at a training range in California and at his remote outpost in Afghanistan — and then returned, according to people briefed on it.

The roughly 35-page report, completed two months after Bergdahl left his unit, concludes that he most likely walked away of his own free will from his outpost in the darkness of night, and it criticized lax security practices and poor discipline within his unit. But it stops short of concluding that there is solid evidence that Bergdahl intended to permanently desert.

Whether Bergdahl was a deserter who never intended to come back, or simply slipped away for a short adventure amid an environment of lax security and discipline and then was captured, is one of many unanswered questions about his disappearance.

The issue is murky, the report said, in light of Bergdahl’s previous episodes of walking off. The report cites accounts from his unit mates that in their predeployment exercise at the Army’s National Training Center at Fort Irwin, Calif., he sneaked or crawled off a designated course or range either to see how far he could go or to see a sunrise or sunset.

The report is also said to cite members of his platoon as saying that he may have taken a shorter unauthorized walk outside the concertina wire of his combat outpost in eastern Afghanistan before he left for good, in an incident that was apparently not reported up the chain of command. The Military Times on Wednesday first reported that claim, also citing officials familiar with the military’s report.

But the report is said to contain no mention of Bergdahl having left behind a letter in his tent that explicitly said he was deserting and explaining his disillusionment, as a retired senior military official briefed on the investigation at the time told The New York Times this week.

Asked about what appeared to be a disconnect, the retired officer insisted that he remembered reading a field report discussing the existence of such a letter in the early days of the search and was unable to explain why it is not mentioned in the final investigative report.

Lt. Col. Todd Breasseale, a Pentagon spokesman, declined to discuss the report or make it available.

“The Department of Defense does not discuss information contained within classified investigations,” he said. “The department is making every consideration regarding the disposition of its continued classification.”

The narrative about Bergdahl over the past few days has undergone a rapid evolution based on accounts by current and former soldiers, growing increasingly darker. They have gone from saying he should not be treated as a hero because he was a deserter and blaming the subsequent search for him for every US combat death in the province over a three-month period, to alleging that there is evidence that he was trying to meet up with the Taliban.

Amid the controversy, a planned celebration in his hometown, Hailey, Idaho, to celebrate his return has been canceled. But the accounts of the investigative report, which was described as meticulous and thorough, suggest that even basic facts necessary to understand how he came to disappear have yet to be definitively established.

The people briefed on the “15-6 report,” named for a section of the Uniform Code of Military Justice covering such investigations, described it on condition of anonymity because it remains classified. The report was written by an investigating officer in July and August 2009 after extensive interviews with members of Bergdahl’s unit, including his squad leader, platoon leader, and company and battalion commanders.

It is said to confirm certain other details relayed in recent accounts, including that Bergdahl shipped his computer and a journal home before he disappeared. It also confirms that he left behind his body armor and weapon — an unwieldy SAW machine gun — taking with him water, knives and a compass.

The report speculates that he likely left in the darkness after the moon had set, following one of two possible routes through the concertina wire.

While much of the report is said to focus on disciplinary problems within his unit and a lack of accountability within its chain of command, the report is also said to portray Bergdahl as a free-spirited young man who read martial-arts books, drank tea with Afghan soldiers from whom he tried to pick up Pashto phrases, and maintained a collection of throwing stars and knives, which it documents in detail.

Its portrayal of him as a soldier is said to be positive, with quotes from both commanders and squadmates — apparently including some of the men now criticizing him — describing him as punctual, always in the correct uniform and asking good questions. It quotes colleagues as saying that he expressed some boredom and frustration that they were not “kicking down doors” more to go after insurgents who were destroying schools.

The report is also said to contain no mention of any alleged intercepts of radio or cellphone traffic indicating that Bergdahl was asking villagers if anyone spoke English and trying to get in touch with the Taliban, as two former squadmates told CNN this week in separate interviews that they remembered hearing about from a translator who received the report.

A leaked military activity report that contemporaneously logged significant events during the initial eight-day search for Bergdahl says that at 10:12 a.m. local time on June 30, about six hours after he was reported missing, an unidentified man was overheard on a radio or cellphone saying that a US soldier with a camera “is looking for someone who speaks English.”

Still, the log says nothing about the unidentified man’s saying that the American wanted to get in touch with the Taliban.